背景：服务端返回的是data，code，info。其中code为0000的时候表示成功。此时data对应正常情况解析json生成的实体类但是当code不为0000的时候，data就是一个String 类型的信息。如果使用官方默认的GSon解析会抛出异常。用rxjava的时候会执行OnError。因为此时类型不匹配。String类型毕竟不是我们自定义的接受json的实体类。

解决方案：不使用retrofit默认的json解析配置，自己参照官方稍微改一下自己写一个（因为官方的那个是final类型的，不允许继承），代码如下 BaseJsonResponse 为自己定义的json对象基类

 final class CustomResponseConverter<T> implements Converter<ResponseBody, T> {
private final Gson gson;
private TypeAdapter<T> adapter;
private Type mType;

 CustomResponseConverter(Gson gson, TypeAdapter<T> mAdapter, Type mType) {
    this.gson = gson;
    this.adapter = mAdapter;
    this.mType = mType;
}
@Override
public T convert(ResponseBody value) throws IOException {

    BaseJsonResponse mResponse = new BaseJsonResponse();
    try {
        String body = value.string();
        JSONObject json = new JSONObject(body);
        Log.e("json", "convert: "+body );

        String code = json.getString("resultCode");
        String msg = json.getString("resultInfo");
        if (code.equals("0000")) {
            return gson.fromJson(body, mType);
        } else {
            return (T) mResponse.setResult(json.opt("result")).setResultInfo(msg).setResultCode(code);
        }
    } catch (Exception e) {
        throw new RuntimeException(e.getMessage());
    } finally {
        value.close();
    }

}}      

public final class CustomGsonConverterFactory extends Converter.Factory {
public static CustomGsonConverterFactory create() {
return create(new Gson());
}
public static CustomGsonConverterFactory create(Gson gson) {
return new CustomGsonConverterFactory(gson);
}

private final Gson gson;

private CustomGsonConverterFactory(Gson gson) {
if (gson == null) throw new NullPointerException("gson == null");
this.gson = gson;
}

@Override
public Converter<ResponseBody, ?> responseBodyConverter(Type type, Annotation[] annotations,
Retrofit retrofit) {
TypeAdapter<?> adapter = gson.getAdapter(TypeToken.get(type));
return new CustomResponseConverter<>(gson, adapter,type);
}

@Override
public Converter<?, RequestBody> requestBodyConverter(Type type, Annotation[]         parameterAnnotations, Annotation[] methodAnnotations, Retrofit retrofit) {
TypeAdapter adapter = this.gson.getAdapter(TypeToken.get(type));
return new GsonRequestBodyConverter(this.gson, adapter);
}
}

然后在创建请求的时候

 public ShowApi createShowApi( ) {
    if (showApi == null) {
        synchronized (RetrofitService.class) {
            if (showApi == null) {
                initOkHttpClient();
                showApi = new Retrofit.Builder()
                        .client(mOkHttpClient)
                        .baseUrl(Constant.Host)
                        .addConverterFactory(CustomGsonConverterFactory.create())
                        .addCallAdapterFactory(RxJavaCallAdapterFactory.create())
                        .build().create(ShowApi.class);
            }
        }
    }
    return showApi;
}